U.S. Pat. No. 5,637,064 to Towley et al, which is assigned to the assignee of this invention, discloses an existing selectorized dumbbell that is known as the PowerBlock®. In this dumbbell, there are eight nested weights each of which comprises a left weight plate and a right weight plate that are joined together by a pair of front and rear rails. The left and right weight plates of the nested weights are disposed in left and right weight plate stacks that are spaced apart from one another by the length of the front and rear rails. The rails of successive nested weights are longer and lower than the rails of the weight immediately to the inside to allow the weights to be nested together in the aforementioned manner.
The selectorized dumbbell disclosed in the 064 patent includes a handle that is dropped down into the gap between the left and right weight plate stacks. Each end of the handle includes a plurality of slots that are located such that one slot is below each of the rails. A selector comprising a U-shaped connecting pin having a pair of spaced, parallel connecting prongs is provided with the prongs of the connecting pin being insertable into the slots beneath the rails of one of the nested weights. When the user then lifts the handle, the handle will carry with it the all of the nested weights whose rails lie above the rail of the selected weight. Thus, the user can easily adjust the total weight carried by the handle, to adjust the exercise mass of the dumbbell, simply by repositioning the connecting pin from one set of slots to another.
A selectorized dumbbell of the type noted above can be adjusted from a minimum weight to a maximum weight. Some users might never progress beyond the maximum weight provided by the dumbbell. However, other users might reach the point where the maximum weight provided by the dumbbell is no longer enough for their exercise needs—their strength has improved so much that they have outgrown the dumbbell they originally purchased. While such a user could then purchase a larger and heavier dumbbell having a higher maximum weight, and manufacturers of such dumbbells would typically offer a few different dumbbells of different sizes for this purpose, the originally purchased dumbbell effectively becomes redundant or unnecessary. In this scenario, the user has obviously had to pay twice to purchase two different dumbbells.
To address this problem, the manufacturer of the PowerBlock® selectorized dumbbell has marketed a kit of add-on weights to allow the user to incrementally add further weight to the originally purchased dumbbell when the maximum weight of that dumbbell is now too light for the user's needs. Such a kit is disclosed in U.S. Pat. No. 5,769,762 which is also owned by the assignee of this invention.
The add-on weights of the 762 patent have a significantly different construction from the weights in the base dumbbell shown in the 064 patent. The add-on weights of the 762 patent still have spaced left and right weight plates, but such weight plates are no longer joined together by a pair of front and rear rails. Instead, the left and right weight plates are joined together by a bottom channel having front and rear walls with the front and rear walls of the various weights in the add-on kit horizontally overlying one another when the weights in the add-on kit are nested together. Various unique sets of holes and slots are placed in the front and rear walls of the channels. A second connecting pin is then inserted through one selected set of such holes and slots to additionally attach a desired number of the add-on weights of the 762 patent to the handle of the dumbbell. The number of such add-on weights that are attached change depending upon which set of holes and slots receives the second connecting pin.
While the 762 patent discloses an effective way of adding more weight to an existing, previously purchased dumbbell, it does require the user to manipulate and position two separate connecting pins, namely the U-shaped connecting pin provided with the dumbbell and the second, single pronged connecting pin provided with the kit of add-on weights. Moreover, each of these connecting pins employs a different pinning technique. The U-shaped connecting pin simply slides into one set of a series of vertically spaced sets of slots provided in the handle to position the connecting pin beneath the side rails of a selected weight in the series of nested weights. On the other hand, the single pronged connecting pin has to be inserted into one set of a series of horizontally spaced sets of holes and slots provided in the bottom channels of the weights themselves. This difference in pinning techniques is potentially confusing, particularly to a relatively new user of the dumbbell.